Opponent After-images

The nature of our visual system allows us to sometimes see "after-images"
which appear once the original stimuli are removed. In the following demonstration, you
will see that the colors in after-images are usually the opposite (complementary) colors
of the original.

Instructions: Stare at the black spot in the center of the four
colored squares for about 30 seconds. Then scroll down and move your gaze to the black
spot in the uniform white area. Note the colors of the afterimages relative to the colors
of the original stimuli. Did they appear different?